Application of computed tomography to assess the effect of egg yolk ratio on body composition in chickens of different genotype and gender at hatch and during the rearing period

Abstract

1. Computed tomography was used for the in vivo determination of yolk ratio in 7000 domestic hen eggs, originated from two markedly different genotypes, in order to examine the effect of egg yolk ratio, gender and genotype on the development of hatched chicks.

2. Eggs with extremely low, average and extremely high yolk ratio were chosen for further investigation (n = 350 in each group in both genotypes). After incubating the selected eggs, hatched birds were reared and slaughtered at 11 weeks of age.

3. The yolk ratio of eggs significantly affected the body composition of the chickens at hatching and during rearing to 8–9 weeks of age.

4. Chickens of a genotype selected partly for weight gain had significantly higher live weight from hatching to the end of the rearing period and had better slaughter characteristics than those of the dual purpose TETRA-H genotype.

5. At hatching, only the dry matter content of the body was affected by the gender of the birds. The effect of gender on the live weight and body composition of chickens was evident from the 5th week of age to the time of slaughter.

6. It was concluded that eggs with a low yolk ratio were most beneficial for broiler production, because chickens hatched from these eggs had the highest slaughter weight and muscle index and the lowest fat index for their body mass.

ACKNOWLEDGEMENTS

This research project was supported by the Hungarian Scientific Research Fund (OTKA NNF 78840) together with the Norwegian Financial Mechanism (Norway Grant) including Padova University as Research Unit.  Authors would also like to thank Marco Cullere and Barbara Contiero of the Department of Animal Medicine, Production and Health of the University of Padova (Italy) for their technical support.